A method of serving a version of a piece of content from a server to a requesting node is described. A request for a piece of content is received from the requesting node. The request comprises an IP address associated with the requested content, the address including one or more portions relating to one or more parameters associated with the piece of content and at least one portion comprises anonymous bits. A plurality of versions of the requested piece of content are identified, each identified version having an IP address with portions matching the corresponding portions of the IP address of the request, except for the at least one portion comprising anonymous bits. The server then determines a version of the piece of content to send and sends the determined version to the requesting node.